Lifting-jack.



.A. B; CHERRY; LIFTING JACK.

APPLICATION FILED APE. 26,1909. 945,489. Patented Jan. 4, 1910. A 2SHEETS-SHEET l.

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LIFTING JACK. APPLICATION FILED APR. 26,1909.

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ALBERT B. CHERRY, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO SAMUEL ASCHER,

.OF BROOKLINE, MASSACHUSETTS, AND THOMAS E. CHERRY, F REVERE, 1VlIASSA-CHUSiETTS.

LIFTING-JACK.

Specification of Letters Patent:

Patented Jan. 4:, 1910.

Application filed April 26, 1909. Serial No. 492,366.

' of Massachusetts, have invented certain new and useful Improvements inLifting-Jacks, of which the following is a specification.

This invention relates to a lifting jack having a lifting bar which ismovable endwise by oscillating movements of an operating lever,adjustable means being employed for causing the movements of theoperating .lcver under one adjustment to progressively raise the liftingbar step by step, and under another adjustment to let down the liftingbar step by step.

The invention has for-its object to pro vide a simple and effectiveconstruction of a jack of this character, and it consists in theimprovements which I will now proceed to describe and claim.

Of the accompanying drawings forming a part of this specification,Figure 1 repre-' sents a side elevation of a jack embodying myinvention, a part of the casing being'removed to show the internalmechanism, the operating mechanism being .adjusted to cause aprogressive upward movement of the lifting bar. Fig. 2 represents a viewsimilar to a portion of Fig. 1, the frame being shown in' section andthe end portions of the tripping lever shown in Fig. 1, being brokenaway. Fig. 3 represents a view similar to Fig. 1 showing the operatingmechanism adjusted to permit a step-by-step downward movement of thelifting bar, the operating lever being depressed. Fig. frepresents aview similar to Fig. 3, showing the operating lever raised. Figs. 5 and6 represent elevations of portions of the jack, the adjustment being asshown in Figs. 1 and 2.

The same reference characters indicate the same parts wherever theyoccur.

In the drawings, 12 represents the frame or casing of the jack, and 13represents a lifting bar which is provided along one of its verticaledges with ratchet teeth 14..

15 represents an operating lever which is fulcrumed at 16 to the casing.

17 represents a lifting pawl which is pivoted at 18 to the shorter armof the operating lever and is normally pressed by a spring 119 againstthe ratcheted edge of the lifting ar.

20 represents a holding pawl which is pivoted at a suitable fixed pointrelatively to the frame or casing. In the drawings said fixed point isthe fulcrum stud 16 of the lever 15. The holding pawl is normallypressed by a spring 22 against the ratcheted edge of the lifting bar,the arrangement of its pivot relatively to the fulcrum of the leverbeing such that the up and down movements of the lever do not cause theholding pawl to eflect any lifting action on the ratcheted bar, so thatthe holding pawl is at all times in position to retain the lifting barin any position to which it is raised by the upward movement of thelifting pawl caused by a downward movement of the operating lever.

23 represents a tripping lever which is fulcrumed at 24 to the liftingpawl 17.

The shorter arm of the operating lever 15 provided with a laterallyprojecting stud 25 which constitutes an, abutment against which thelower arm of the tripping lever bears when said tripping lever is in itsoperative adjustment.

26 represents a stud or projection on the holding pawl 20, saidprojection being operatively engaged with an inclined edge 27 on theupper arm of the tripping lever 23 when said tripping lever is in itsoperative adjustment.

28 represents a rod which is longitudinally movable in a slot 29 formedin the wall of a circular boss 30 on the frame 12, said rod beinglongitudinally movable in said slot and provided at its inner end with ahead or abutment 31 on which bears one end of a spring 32 whichsurrounds the inner end portion of the rod. The other end of saldspring-bears upon an ear or wing 33 which forms a part of the trippinglever 23, said wing having a slot or opening 33 (Flg. 1) through whichthe rod 28 passes loosely. Said spring 32 is of a strength greater thanthat of the spring 22 which presses the hold-, ing pawl against bar 13,so that when said sprin 32 is permitted to act, as hereinafter descried, the holding pawl will be d1sengaged from said bar to permit loweringof the latter.

When the rod 28 is pushed inwardly as shown in Fig. 1, the spring 32 isremoved from active bearing pressure on the tripping lever so that thelatter is free to assume the inoperative position shown in F g. 1, itslower arm being out of contact with the abutment 25 and its upper armbeing so related to the projection 26 on the hold ing pawl that it doesnot affect said pawl. When the rod 28 and the tripping lever are in theposition last described, both pawls bear continuously on the ratchetededge of the lifting bar, the jack being therefore adjusted to cause astep-by-step elevation of the lifting bar and its load, the pawls simplyyielding, as required, against their springs 19 and 22. Vhen the rod 28is pulled outwardly as shown in Figs. 3 and 4, the spring- 32 iscompressed so as to bear actively on the tripping lever and hold thelower arm of the latter in engagement with the abutment 25 on theoperating lever, the tripping lever being therefore in its operativeposition to permit lowering of the bar 13. This compression of thespring causes the tripping lever to oscillate on its fulcrum 24 underthe influence of the spring 32 but controlled by the abutment 25 of theoperating lever 15. When the outer end of the operating lever 15 isdepressed as in Fig. 3, the abutment 25 occupies a position whichpermits the spring 32 to press the upper end of the tripping lever 23back so that the edge 27 of said lever 23 acts against the stud 26 ofholding pawl 20 to press thelatter yieldingly out of engagement with theratchet bar 13. The pawl 17 is now holding the bar 13. Upon actuatingthe operating lever to the Fig. 4 position, the pawl 17 first lets thebar 13 down and then the abutment 25 causes the lever 23 to oscillate soas to further compress the spring 32 and permit the spring 22 to throwthe holding pawl 20 back to the ratchet bar. During the last part ofthis lowering movement, the conjoint action of abutment 25 and spring32, acting in the same direction on-both ends of the lever 23, overcomesthe power of spring 19 and presses the lever 17 away from the ratchetbar because the lever 23 and pawl 17 are pivotally connected at 24. Atthe beginning of the next movement from the Fig. 4 to the Fig. 3position, the swinging of the abutment 25 somewhat away from the lowerend of lever 23 relieves the force which spring 32 is causing at thepivot 24 so that the spring 19 can return the pawl 17 into engagementwith a tooth of the ratchet before the further movement of the operatinglever causesfthe release of the holding pawl 20 in the manner alreadydescribed. It will be seen therefore, that, when the tripping lever isin its operative adjustment the movements of the operating lever cause astep-bystep downward movement of the lifting bar and its load.

The rod 28 is provided with a projection 'orflatch member 34, adapted toengage a notch 35 in the perimeter of the boss 30 ,whe nlfltheg'rodisdrawn outwardly, the rod being'thus'retained in its outward position asand caused to'retain thetripping lever in its operative position. Thenotch 35 is locatedat one end of a cam face 36 on the boss 30, said camface being so formed that, when the rod is moved from the position shownby dotted lines to that shown by full lines in Fig. 6, the cam face willpermit an inward movement of the rod to the-position shown in Fig. 1.

It will now be understood that, owing to the structure including thetripping lever and the spring 32, the pawls are both forced yieldinglyand successively out of engagement with the bar 13 when the latter isbeing lowered, and consequently there is compensation for wear of thepawls and ratchet teeth which would not be the case if the out wardmovement were effected by mechanism acting positively on the pawls. Myimproved structure is such that springs are permitted to act at therequired times to shift the pawls both in and out, and therefore theaction will remain the same even after considerable wear of the movingparts.

I claim l 1. A lifting jack comprising a frame, a ratcheted lifting barmovable therein, an operating lever fulcrumed on the frame and having anabutment on its shorter arm, a lifting pawl pivoted to the shorter armof the operating lever, a holding pawl having a projection, means fornormally maintaining the pawls continuously against the lifting bar, atripping lever fulcrumed on the lifting pawl at a point between the'abutment on the lever and the projection on the holding pawl, saidlever being movable on its pivot to bring its end portions into and out,of operative engagement with said abutment and projection, and adaptedto trip the pawls alternately when in said operative engagement,. andmeans for moving the tripping lever to and from its operative position.

2. A lifting jack comprising a frame, a ratcheted lifting bar movabletherein, an operating lever fulcrumed on the frame and having anabutment on its shorter arm, a lifting pawl pivoted to the shorter armof the operating lever, a holding pawl having a projection, means fornormally maintalning the pawls continuously against the lifting bar, atripping lever. fulcrumed on the lifting pawl at a point between theabut ment on the lever and=the-projection on the holding pawl, saidleverbeing movable on its pivot to bring its end portions into and outof operative engagement with said abutrod and bearing on the trippinglever, the

rod'b'eing movable longitudinally outward to compress the spr ng andcause it-toyhold the tripping lever in its operative position, and meansfor detachably securing the rod in its outward position, the rod, whenmoyed inwardly, permitting the tripping lever to assume its normalinoperative position.

3. A lifting jack comprising a frame having a slotted cam-shapedexternal portion and a notch atone end thereof, a, ratcheted lifting barmovable in the frame, a holdingpawl, a lifting pawl, an operating leverfulcrumed on, the frame, means for normally maintaining the pawlscontinuously against the lifting bar, said pawls being adapted tonormally cause a step-by-step elevation of the latter through the opera-1 tion of the lever, ,a tripping lever movable by the operating leverand adapted to trip 1ng rod connected with the trim iing lever andextending through the slot in the casing, said rod having a projectionwhich is adapted to engage the notch in the casing to confine the rodand is movable on the said cam-shaped portion, the latter permitting aninward endwise movement of the rod, and a spring connected to said rodand bearing against the tripping lever, substantially as described.

In testimony whereof I: have affixed my signature, in presence of twoWitnesses;

ALBERT I). CHERRY.

\Vitnesscs:

' C. F. BROWN,-

